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THE VOYAGE OF H.M.S. CHALLENGER. 
CHAPTER XVI. 
Hong Kong to Manila and Zebu — Mactan and Zebu — Zebu to Camiguin Island and Samboangan — Samboangan — 
Samboangan to Humboldt Bay — The Polyzoa — Cephalodiscus — Humboldt Bay — Humboldt Bay to the Admiralty' 
Islands — The Alcyonaria- — The Nudibranchiata. 
Hong Kong to Manila. 
On the 6th January 1875, the Challenger left Hong Kong just before noon, steam- 
ing out to the eastward through the Lyemun Pass ; then between the Tathong Rock 
and Hong Kong Island for the channel between Sunkong and Pootoy Islands, after pass- 
ing through which the ship was steered for the northeast head of Lema Island, which 
was passed at 3.30 p.m., when sail was made and the fires put out. 
On the 8th the wind, which had been blowing fresh from the northeast, moderated 
sufficiently to allow of sounding and trawling, at 11 a.m., in 2100 fathoms (see Sheet 31). 
The temperature at the bottom proved to be precisely the same as that at 900 fathoms, 
indicating that the China Sea is cut off from the Pacific Ocean by a ridge of about 
that depth. At 5 p.m. the trawl was hove up, and sail was again made towards 
Manila. 
On the 9th, the wind having fallen light and hauled to the eastward, sails were 
furled, and the ship proceeded at 4 p.m. under steam. 
On the 10th, at 8 a.m., the land about Yba was seen, and the vessel was steered to 
the southward as necessary. At 3 p.m. a dismasted vessel was sighted to the eastward, 
which proved to be an abandoned coaster named the “ Santa Maria,” and being 
dangerous to passing vessels was taken in tow. At 5 p.m. Point Silanguin bore S. 48° E., 
and Point Botolan N. 84° E. 
On the 11th, at 4.30 p.m., the vessel anchored in Manila Bay in 4 % fathoms, with 
the Mole lighthouse N. 48° E., the Cathedral N. 70° E., and Cavite light S. 20° W. 
On the passage from Manila to Hong Kong, as well as on this the return voyage, the 
surface temperature was found to be 3° higher within 60 miles of the coast of Luzon 
than it was at a greater distance from that island, and this change of temperature was 
sudden, taking place in the voyage to Hong Kong in a distance of 10 miles, and in the 
return voyage in 6 miles. On each occasion, so long as the ship was in the belt of 
warm water, a northerly current was experienced. This stream is shown on the Current 
Chart of the World, published in 1872, but on the chart of the China Sea (northern 
portion, sheet 2) a current arrow is drawn as if a S.S.W. set were always experienced in 
the neighbourhood. The source of this warm current on the Luzon coast has not 
